Fenestration assemblies are typically installed in rough openings in structures. A gap is typically maintained between the fenestration assembly and the rough opening to accommodate expansion and contraction of building materials throughout temperature changes, as well as overall shifting and settling of the structure. Water, such as airborne moisture and liquid water in the form of rainwater, ice, snow can penetrate into the building wall interior from in and around building fenestration assemblies.
Attempts have been made to prevent entry of water into the building wall interior by sealing or caulking entry points in and around fenestration assemblies as the primary defense against water intrusion, or by installing flashing around the fenestration assemblies to divert the water. These attempts have not been completely successful. Sealants are not only difficult and costly to properly install, but tend to separate from the fenestration assembly or wall due to climatic conditions, building movement, the surface type, or chemical reactions. Flashing is also difficult to install and may tend to hold the water against the fenestration assembly, accelerating the decay.
The efficiency of such weatherproofing relies largely on the careful installation of both the fenestration assembly and the weatherproofing materials. However, no matter how carefully installed, moisture may enter into gaps between the fenestration assembly and the rough opening. Moisture penetration may be due to shifting or expansion/contraction of materials post-installation.
Such moisture typically collects below the fenestration assembly, where it can cause rot and other undesirable damage to both the fenestration assembly and the structure below the fenestration assembly. In some situations attempts to prevent water penetration around fenestration assemblies may actually trap the water within the structure, exacerbating the problem.
Various drain holes systems for fenestration assemblies have been used to divert water from the structure, such as disclosed in U.S. Pat. Nos. 3,851,420 (Tibbetts); U.S. Pat. No. 4,691,487 (Kessler); and U.S. Pat. No. 5,890,331 (Hope).
Specialized flashing structures have been developed for installation in the gap between the rough opening and the fenestration assembly. Examples of such specialized flashing structures are shown in U.S. Pats. No. 4,555,882 (Moffitt et al.); U.S. Pat. No. 5,542,217 (Larivee); and U.S. Pat. No. 6,098,343 (Brown et al.). U.S. Pat. No. 5,822,933 (Burroughs et al.) and U.S. Pat. No. 5,921,038 (Burroughs et al.) disclose a water drainage system with an angled pan and a plurality of ribs that is located underneath a fenestration assembly.
These specialized flashing structures, however, do not effectively remove water from the interior of the structure. Additionally, the installation of moisture guards often requires changes in the way the fenestration assembly is installed into the rough opening and how the fenestration assembly is finished on the room side so as to accommodate the vertical height of the angled pan. Furthermore, the gap between the fenestration assembly and the rough opening must be sufficient to accommodate the raised end of the angled pan.
The Installation Instructions for New Construction Vinyl Window with Integral Nailing Fin published by Jeld-Wen, Inc. discloses installing a 6″ tall section of screen to the exterior of the structure below the fenestration assembly. The screen extends about the width of the fenestration assembly and is located on top of flashing tape and building wrap. Another layer of flashing tape is applied to the top of the screen. The screen, however, forms one contiguous channel that is too large to permit effective drainage of water.